basic python question about for loop

[Diez B. Roggisch]

jmDesktop schrieb:
> On Apr 9, 4:58 pm, "Diez B. Roggisch" <de... at nospam.web.de> wrote:
>> jmDesktop schrieb:
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>>> From the Python.org tutorial:
>>>>>> for n in range(2, 10):
>>> ...     for x in range(2, n):
>>> ...         if n % x == 0:
>>> ...             print n, 'equals', x, '*', n/x
>>> ...             break
>>> ...     else:
>>> ...         # loop fell through without finding a factor
>>> ...         print n, 'is a prime number'
>>> ...
>>> 2 is a prime number
>>> 3 is a prime number
>>> 4 equals 2 * 2
>>> 5 is a prime number
>>> 6 equals 2 * 3
>>> 7 is a prime number
>>> 8 equals 2 * 4
>>> 9 equals 3 * 3
>>> first time 2 mod 2, 2/2, no remainder == 0, what am I doing wrong?
>>> Why did it fall through?
>> print out what range(2, n) for n == 2 is.
>>
>> And if you didn't know - 2 *IS* a prime.
>>
>> Diez- Hide quoted text -
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>> - Show quoted text -
> 
> I do not understand.

for <variable> in <sequence> loops over a sequence. And of course it 
doens't if the sequence is empty, because you can't loop over something 
that is empty, can't you?

and range(2,2) is the empty sequence.

Diez